NARI Single-Crystal High-Temperature Shape-Memory Alloys · NARI Single-Crystal High-Temperature...

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Single-Crystal High-Temperature Shape-Memory Alloys

ARMD Seedling Fund Phase IPI: Glen Bigelow – GRC RXA

Collaborators:Dr. Jon Goldsby – GRC RXC

Dr. Anita Garg – University of ToledoDr. Ronald Noebe – GRC RXA 1

Shape Memory Alloys Enable the

DevelopmentAdaptive Structures

Variable Geometry Chevron

Variable Geometry

Aerodynamic Surfaces

Flaps, Tabs, Vortex Generators

Smart Fastening

Systems

Reconfigurable Blades

Variable GeometryInlets

Variable Area Fan Nozzle

Objectives

• Grow high-temperature, high purity, shape-memory alloy (SMA) single-crystals using the Czochralski method

• Analyze composition, microstructure, and orientation using electron microscopy and X-ray

• Perform thermo-mechanical testing on samples and compare to polycrystalline and Bridgeman-grown single-crystal samples

Shape Memory Behavior

HeatingWire Contracts

CoolingWire Extends

Weight

Shape Memory Alloy Wire Actuator

∫= εσdW

Temperature (oC)

Permanent Deformation

Heating Curve

Cooling Curve MfAs

TransformationStrain

Measure:a)Transformation Temps Mf, Ms, As, Afb)Transformation Strain -> Work Outputc)Unrecovered Strain -> Dimensional Stability

Load-Biased Strain Recovery Test

Unrecovered Strain

High force (per volume/weight)CompactEasily integrated on existing systemsEliminates extraneous systems• hydraulics, pneumatics, mechanical

Robust Simple, frictionless, quietLow Maintenance

IDEAL FOR HIGH FORCE, LARGE STROKE, LOW CYCLE

Motor: Torque 66 in-lbs

25 lbs

Gear box :190 in-lbs16 lbs

Advantages of SMA-Based Actuation Systems

SMA Rotary Actuator :150 in-lbs

Opportunities for SMA Actuators on Jet Aircraft

Active Winglet

Variable Geometry Chevron/ Variable Area Nozzle

Vortex GeneratorGurney Flap

Access Panel Fasteners

In-Cabin Locks and Fasteners

Maximum Work Output of Polycrystalline SMAs

The Innovation

• HTSMAs – high work output in a small volume• Single-crystal HTSMA’s – high stress capability &

tailorable properties– High transformation strain - high work at low(er) stress– Extreme stress capability – high work output while

maximizing compactness

June 5-7, 2012 NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar 8

Background

• Russian Ni-Ti-Hf SX HTSMA previously tested– Produced by Bridgeman method in graphite crucible– Large carbides due to reaction with carbon in crucible– One-off lab experiment– Future collaboration not feasible

• GRC tri-arc Czochralski grower– Three arcs aid temperature uniformity– Copper cold-hearth – eliminates additional carbon

contamination

Single Crystal Growth Methods• Bridgeman Method Czochralski Method

10*Springer Handbook of Crystal Growth, (2010) Springer-Verlag, Berlin Heidelberg, p288

Czochralski Growth Chamber

SMA Ingot With Pull Rod and Arc Melting Stingers

Tri-Arc Czochralski Method

Single-Crystal Growth Movie

Results

• Crystals of Ni-Ti-Hf, Ni-Ti-Pd, & Ni-Ti-Zr grown• Nucleated using Al2O3 rod, then W• ~3mm rod used to grow Ni-Ti-Pd• Switched to larger 6.3mm rods

1st Gen Ni-Ti-Pd Crystals Already Grown

2nd Gen Ni-Ti-Hf Crystals

Samples and Growth Banding

• Growth banding– Occurs in all CZ

crystals– Can be due to

temperature fluctuations

• (not a problem)

– Or chemical inhomogeneity

• (problem?)

Banding Effects in Ni-Ti-Hf

Ni-29.7Ti-20Hf

• As Grown– Broad – banding – Low Tf – Ni

• Heat treated– High, narrow Tf– Similar in

polycrystal and single-crystal

Ni-49.7Ti-30Pd

• As Grown– Broad – banding– Low Tf – Ni

• Heat treated– High, narrow Tf– Similar in

polycrystal and single-crystal

SEM of Ni-49.7Ti-30Pd

• Banding visible– Martensite in bands

• Also particles– W– TiC

SEM of Ni-29.7Ti-20Hf

• Particles present• 1) TiC 2) HfC• 3) W

• Much smaller in GRC CZ grown SX

• Russian crystal grown in graphite crucible

CZ NiTiHf

Bridgeman NiTiHf

Chemical Analysis ComparisonFeedstock and Single Crystal (SX)

Table 1: Chemical Analysis of HTSMA Single Crystal Samples and Precursor Hot Top Material (at%).

Sample Ni Ti Hf Zr Pd WNiTiHf Feedstock 50.22 29.17 20.14 0.33

SX Hf T 50.2 29 20.4 0.30.15

SX Hf B 50.2 29 20.3 0.310.16

NiTiPd Feedstock 20.01 48.9 31.09

SX Pd B 19 48.9 0.04 31.80.28

Sample composition measured from top (near pull rod) and bottom (near melt)Composition of samples is equivalent to that of the original hot top material.

Transformation Strain Ni-29.7Ti-20Hf

• Moderate TfS– Higher than

Russian SX– Extremely

high stress capability

June 5-7, 2012 NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar 22Temperature (oC)

Heating Curve

Cooling Curve MfAs

Unrecovered Strain

Work Output Ni-29.7Ti-20Hf

• Work is high due to high stress capability

Dimensional Stability Ni-29.7Ti-20Hf

• Stability

equivalent

to that of

Russian Russian

crystals

Heating Curve

Cooling Curve Mf

Unrecovered Strain

Transformation Strain Ni-49.7Ti-30Pd

• Moderate TfS– Lower than

polycrystal– High stress

capability

Heating Curve

Cooling Curve MfAs

Unrecovered Strain

Work Output Ni-49.7Ti-30Pd

• Work is high due to high stress capability

Dimensional Stability Ni-49.7Ti-30Pd

• Stability greater than polycrystal

Heating Curve

Cooling Curve MfAs

Unrecovered Strain

Remainder of Phase I• X-ray in progress to confirm orientation and

quality of crystals, ie low angle boundaries• Mechanical testing of remaining crystals

– Ni-Ti-Zr, and several additional Ni-Ti-Hf

Payoffs/Impact of Innovation• Tailorable properties

– High force (stress)– High displacement (transformation strain)– Hybrid properties

• Properties unobtainable in polycrystalline materials

Summary of Accomplishments

• Successfully demonstrated Czochralski process for fabricating oriented SMA crystals– High stress capability– High work output

• Cleanest SX grown– Lower amount of TiC/HfC– Finer sized particles

Plans for Dissemination

• Enough data for one paper/TM after additional tests are completed

• Conference presentation FY13

Next Steps – Phase II

• Determine growth conditions for producing large (>6mm) and small (<2mm) diameter single-crystals

• Produce crystals of two different orientations– Seeding– Cutting to orientation (requires larger crystals)

• Deliver growth conditions, microstructure, and property data for two sizes and two orientations of single-crystals

• Produce HTSMA SX using carbon-free feedstock32

Ultimate Phase II Goal

• Grow crystals that are several inches in diameter!!

• Next step for single-crystal SMAs to be Commercially Feasible

NARI Single-Crystal High-Temperature Shape-Memory Alloys · NARI Single-Crystal High-Temperature...

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